The present invention relates to a quality control system for a plurality of medical diagnostic apparatuses existing on a network. More particularly, the present invention relates to a quality control system for controlling centrally image qualities of medical diagnostic apparatuses including image input devices and image output devices for medical diagnostic applications.
Various diagnostic apparatuses have heretofore been used in the medical field employing X-rays and other radiations. In radiology, X-rays passing through an object are detected and an image is generated for diagnostic purposes. Images taken by chest radiography have been used widely for quite many years.
Apparatuses relying upon CR (computerized radiography), CT (computerized tomography) and MRI (magnetic resonance imaging) are in commercial use. The images generated by these apparatuses are either displayed on CRT (cathode ray tube) displays or outputted on films by LP (laser printers) or the like for subsequent use in medical working fields to diagnose diseases.
Radiographic and other medical diagnostic apparatuses are making progressive shift toward digitizing. By the “digitizing” is meant a process in which the X-ray signal passing through an object is converted to a digital signal, which is appropriately processed to generate an image suitable for diagnosis.
In line with the highly advanced technologies of communications and computers of recent years, a network utilizing computers has been constructed within a hospital by connecting various medical diagnostic apparatuses described above onto the network.
In the apparatus for CR, there is used a stimulable phosphor which, upon irradiation with a radiation, accumulates part of its energy and upon illumination with exciting light such as visible light or laser light, produces stimulated light emission in accordance with the accumulated radiation energy. The radiation image information about an object such as the human body or the like is first recorded in a sheet of stimulable phosphor (commonly called as “a stimulable phosphor sheet”), which is then scanned with exciting light such as laser light or the like to produce stimulated light which is read photoelectrically as an electric signal, producing an image signal.
When CR is connected to the above-described network, such radiation image recording and reading system may not be connected to the network in its entirety but only an image reading device which reads an image recorded in the stimulable phosphor sheet may be connected to the network thereby inputting the image signal into the network.
In order to prevent a wrong diagnosis, the above-described medical diagnostic apparatuses are required to have a strict display performance; thus, quality control of these medical diagnostic apparatuses is important.
For example, performance of the image reading device to read the X-ray radiograph is characterized by sensitivity, granularity, S/N (signal to noise ratio) or the like. The quality of the image reading device as to what performance the device has can be checked by comparing a relationship between characteristic values (such as RMS (Root Mean Square), DQE (Detective Quantum Efficiency) or the like) computed from the image data obtained by reading the stimulative phosphor sheet on which an image was recorded with X-ray in radiation and X-ray radiation dose to be illuminated on the stimulative phosphor sheet, with the predetermined values which have preliminarily been set.
Moreover, the quality (image quality of a displayed image such as a brightness and resolution characteristics or the like) of a soft copy display device (output device) such as CRT, LCD or the like can be checked by a visual evaluation employing a test pattern or the like such as SMPTE pattern which can check various image qualities comprehensively. However, the qualities of medical diagnostic apparatuses have conventionally been checked individually such that the image quality is checked every time the image quality test is performed, for example, when represents one of the qualities of medical diagnostic apparatuses; and image qualities of a plurality of medical diagnostic apparatuses connected onto the network have not been controlled as a whole.
Therefore, in an institution, such as a large hospital, where a number of medical diagnostic apparatuses are installed, though there has been a necessity for controlling qualities of apparatuses such as image quality level and the like of an image input device (reading device), an image output device (display device) and the like as a whole, respective devices only hold respective results of quality checks individually. In other words, efficiency has been very low in the conventional quality control.